In the present work, a continuous flow micro-structured reactor was used for the preparation of peracetic acid (PAA) in the presence of ultrasonic irradiations. The effect of several parameters such as acetic acid: hydrogen peroxide molar ratio (1:0.45-1:2.5), flow rate (20-40 mL/h), temperature (20-60 degrees C) and catalyst loading (340-707 mg/cm(3)) were investigated in the presence of ultrasound during the preparation of peracetic acid. The deactivation of the Amberlite IR-120H catalyst was studied in micro-structured reactor. The optimum values of the molar ratio of acetic acid:hydrogen peroxide, flow rate, temperature and catalyst loading were found to be 1:1, 30 mL/h, 40 degrees C and 471 mg/cm(3), respectively. In the present study, the reaction time observed was less than 10 min compared to that of conventional batch reactors. This drastic decrease in the reaction time was attributed to the use of micro-structured reactor in which heat and mass rates are significantly higher compared to conventional reactors. Also, use of ultrasound drastically enhances the reaction rate due to the formation of H2O2 from the chemical effects of ultrasound. (C) 2015 Elsevier B.V. All rights reserved.